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Wednesday, May 18, 2011

Caveat emptor! The latest snake oil being hawked by geneticists.

The British newspaper The Independentreported on May 16 that a £435 ($700) test to determine telomere length will go on sale in Britain within the year. Telomeres are structures on the tips of chromosomes that have been found to shorten with age, and the company, Life Length, claims that the test results will predict a person's lifespan.

Scientists behind the €500 (£435) test said it will be possible to tell whether a person's "biological age", as measured by the length of their telomeres, is older or younger than their actual chronological age.

Life Length is anticipating hundreds of requests from people wanting to have their telomeres tested and is expecting demand from thousands more once the company is able to bring down the cost of the test as public demand increases.

And they are certain that public demand will increase.

Asked why the general public would be interested in taking a telomere test, Dr Shay [a consultant to Life Length] said: "I think people are just basically curious about their own mortality. If you ask people what they worry about, most people would say they are worried about dying."

He added: "People might say 'If I know I'm going to die in 10 years I'll spend all my money now', or 'If I'm going to live for 40 more years I'll be more conservative in my lifestyle'.

Curiously, the reporter adds, "The worrying thing is that if this information ever got to a point where it is believable, insurance companies would start requiring it in terms of insuring people." Throughout the story the reporter strives to be agnostic as to whether the science is up to the claim, quoting scientists on both sides of the issue (though, it must be said that those in favor are tied to Life Length) and yet he apparently doesn't believe it himself. Why isn't that the story here? Why give free advertising to a product that isn't obviously ready for prime time?

Indeed, a follow-up story in the same newspaper by the same reporter on May 17 under the headline "Concerns grow over DNA test that determines your lifespan", tells a more cautionary tale.

Experts are worried that people may misunderstand the limitations of the test, which purports to measure a person's true "biological" age rather than the usual chronological age. They are also concerned that the information may be used by insurance companies and organisations trying to sell fake anti-ageing remedies.

"I'm sceptical and concerned about this test mainly because of the lack of evidence that this information is useful and yet this test touches on really significant issues, such as predictions of life expectancy," said Colin Blakemore, an Oxford neuroscientist and former head of the Medical Research Council.

"My pressing concern is just how reliable these tests are in terms of anything significant. We need to know an awful lot more before we make predictive statements. People worry about how predictive it is."

This sounds an awful lot like what's being said by some about direct-to-consumer genetic testing companies. We, for example, have said it here, and here. How predictive genes 'for' disease or telomere length actually are is simply not known, and sales of these results as though it is is just snake oil.

Yes, telomere length has been found to be correlated with lifespan, but as everyone knows, correlation does not mean causation. Which comes first, illness which shortens telomeres, or short telomeres, which cause illness?

And even more significant for this story is the fact that apparently telomeres can be lengthened. A paper published in The Lancet in 2008 looked at telomerase activity (the enzyme that maintains telomeres) in men with low-risk cancer of the prostate.

30 men with biopsy-diagnosed low-risk prostate cancer were asked to make comprehensive lifestyle changes. The primary endpoint was telomerase enzymatic activity per viable cell, measured at baseline and after 3 months. 24 patients had sufficient PBMCs [peripheral blood mononuclear cells] needed for longitudinal analysis. This study is registered on the ClinicalTrials.gov website, number NCT00739791.

And, telomere length has been linked with chronic stress exposure and depression. Indeed, some studies have shown, according to the May 16 story, "that meditation or other forms of stress reduction may lengthen telomeres" (one such study is here). Even some of the pro-testing scientists interviewed for the story suggest that people who find out they have short telomeres can beat the odds by improving their diet and exercising. So, why should anyone buy this $700 test if telomere length is essentially a reflection of lifestyle, and a short term one at that?

And that's just the beginning. Other issues include the variance around the predicted (statistically 'expected') age of death. And how stable that is--since it must be based on actual deaths in some way, relative to the dynamics of telomere degradation per year. And whether death-age estimates are based on prior lifestyle exposures which cannot be extrapolated to the future. And whether the prediction is any better than that based on your close relatives' experience, your weight, diet, smoking and other habits, your job hazards, and so much else.

Telomeres are important aspects of genomic health, but organismal health is more complicated than just telomere length (measured in blood samples, whereas death rarely occurs because of blood failure!). There are correlations with body size and lifespan, but the relationship to telomeres and their maintenance across species and over evolutionary time are not so simple.

So, snake oil is still snake oil. Caveat emptor! And scientists: be restrained in what you accept and what you teach your students.

Someone needs to do a study of the genetics of palm-reader's criteria and see if they're actually associated with longevity, or telomere length. Genes probably make some contribution to the length of lines on palms, after all. And if the lines are associated with longevity....we can start a new genotyping service company.

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